Credentials may be used to determine whether or not persons are who they say they are. Assume, for instance, that a man walks up to a bank teller and says his name is “J. Warren Smalley” and that he would like to withdraw two hundred dollars from a checking account held by J. Warren Smalley. The bank teller may use a credential to determine if this man really is J. Warren Smalley. Banks often use documentary credentials, like a passport or drivers license having a photo and name. If this man looks like the man pictured on the document and the document says that the picture is of J. Warren Smalley, the bank may authenticate that this man really is J. Warren Smalley.
The bank may also use other types of credentials, like a secret or something unique to a particular person. The bank may authenticate that this man is J. Warren Smalley if they have a record showing J. Warren Smalley's signature—something unique to J. Warren Smalley—and this man's signature matches the signature on the record. The bank may also authenticate this man with a secret, like a password. Thus, if this man submits to the bank teller a personal identification number (PIN) matching the PIN for J. Warren Smalley, the bank may authenticate that this man is who he says he is.
Computers also interact with people to identify them, often using a name/password pair as their primary credential to do so. Many computer operating systems, for instance, require a user to submit a password for authentication. To enable this interaction, the operating system may present a graphical user interface. This interface may show accounts associated with various users, enable the person to select one of these accounts, and enable entry of a password for the selected account. The operating system may then receive an entered password and authenticate that this password identifies a user associated with the selected account. The operating system may then log that person on, permit a certain action, or the like.
This graphical user interface, however, often enables only a single credential type—a username and password—by which a user may be authenticated. This can be a problem if other credential types are desired or later developed. If some company develops a credential type that is superior to or at least useful in conjunction with a username/password credential, the company may have to create a new graphical user interface to enable use of this credential type. Assume the company develops a type of credential based on a person's thumb print. The company may sell scanners that scan people's thumbs and software capable of authenticating that a scanned thumb matches a particular person. To enable computers to use this credential however, the company may have to write a new user interface replacing password-based ones often used by computers. This new user interface may take many weeks or months for skilled programmers to design.
Also, even if a company designs this new user interface, another company may come along with another credential type, such as a retina-based credential. In this case, the retina-scanning company may need to create another user interface for computers to use its retina-based credential. And this user interface may not be able to handle a thumb-print-based credential. If a corporation or the government wants to authenticate a person with a password, a thumb print, and a retina scan, it may not be able to do so without creating yet another user interface costing even more time and effort.